1. Field of the Invention:
This invention relates to slide gates for controlling fluid flow and, more particularly, is directed toward an improved slide gate and slide gate seals.
2. Description of the Prior Art:
Slide gates are employed to control fluid flow through a passageway or channel. A slide gate has a frame assembly which defines an opening through which fluid flows, a slide plate slidably mounted to the frame assembly and adapted for vertical movement relative thereto so as to selectively open and close the opening, a sealing member for providing a watertight seal between the slide plate and frame assembly, and operating means for vertically moving the slide plate between open and closed positions for regulating fluid flow through the opening. Generally, the frame assembly is mounted to the walls surrounding or defining the passageway or channel through which the fluid flows in such a manner that substantially all of the fluid flow passes through the opening in the frame assembly. In this way, fluid flow through the opening of the slide gate is determined by the position of the slide plate within the frame assembly. Typical slide gates are shown in U.S. Pat. Nos. 3,760,593; 4,028,896; and 4,226,533.
Slide gates have been met with varying degrees of success due to a number of disadvantages and limitations associated with the seals which are used to provide a watertight connection between the slide plate and the frame assembly. The most common type of seal presently in use is the resilient bulb seal, generally known as the P-type or J-type seal. Bulb seals have a flat elongated body with an enlarged hollow or solid bulb at one end. The flat body of the seal is sated within the frame assembly and the enlarged bulb is compressed between the movable slide plate and the frame assembly. The compressed bulb fills the region between the slide plate and the frame assembly and provides a watertight seal, while allowing movement of the slide plate relative to the frame assembly. In other cases, the compressed bulb seal is positioned between the slide plate and the wall surrounding the passageway or channel through which the fluid flows.
In either case, due to frictional contact between the bulb and the slide plate, the compressed bulb has a tendency to bind with and restrict the movement of the slide plate. In consequence, heavier and stronger operating means are required to move the slide plate for opening and closing the slide gate. Also, the excessive frictional contact between the seal and slide plate results in high operating forces being required and in premature failure of the seal. Furthermore, the bulb portion of the seal tends to dam fluid (and any debris carried by the fluid) about the seal and impede fluid flow through the slide gate when the slide plate is in its unblocking or open position. Prior to the present invention, seal retainers required at the sides of the slide gate were costly to produce, laborious to install and repair, and unpredictable with respect to the amount of drag produced on the slide plate.
Alternative seal designs, which do not use a compressed bulb, have suffered from the disadvantages that they are not watertight seals. Also, these seals are short-lived, costly to manufacture and difficult to install. Slide gates which use stainless steel extruded frame members have met limited degrees of success. Stainless steel extrusions generally are not consistent in size and slide gates using such extrusions are characterized by poor sealing.